Friday, 18 August 2017

A constructor
in Java is a block of code like to a method that's invoked when an
instance of an object is created.

Every class has a constructor,
if we don't clearly declare a constructor for any java class the compiler
builds a default constructor for that class.

Main difference
between method and constructor is constructor does not have any return type.

Constructor in Java
can’t be abstract, static, final or synchronized.

Two types of
constructor available in java

Default Constructor

Parameterized constructor

Default constructor :

Default constructor is
when we don’t pass argusment to the constructor.

If we don’t create the
lib automatic create blank contructor.

Code

class myclass

{

myclass()

{

System.out.println("this
is constructor");

}

public static void main(String
args[])

{

myclass m = new
myclass();

System.out.println("this
is main method");

}

}

Output:

this is constructor

this is main method

Parameterized constructor

In parameterized constructor we pass argument or
parameter in constructor.

Code

class myclass

{

int a,b;

//parameterized constructor

myclass(int x,int y)

{

a
= x;

b = y;

}

public static void main(String
args[])

{

int
c;

myclass m = new
myclass(12,22);

c = m.a + m.b;

System.out.println("c
: "+c);

}

}

Output:

c : 34

Constructor
overloading

Like
Methods, Constructors could also be overloaded. Since the Constructors in a
Class, all have the same name as the C Constructor overloading is not a lot
different than method overloading. In case of method overloading you have
multiple methods with same name but dissimilar signature, where in Constructor
overloading you has numerous constructors with different signature but only
difference is that Constructor doesn't have return type in Java. lass, their
signatures are differentiated by their argument lists.

So
in this post we learned constructor in java.and constructor overloading.